Inside, a steamy pungence of physical and emotional exhaustion fills Studio B. Slowly pacing the mirrored wall along the front of the studio is Pandit Chitresh Das.

With his hands on his hips, Das’ taut, discreetly muscular dancer’s physique peeks out from under his short sleeves draped in simple yet coarsely elegant black cotton.

The revered 68-year-old master of Kathak — an ancient flavor of Indian classical dance — has arrived early this afternoon, just in time to shower disappointment on an intermediate class of aspiring Kathak dancers, all young women, most in their late teens:

“You don’t believe in your own heritage. If you believed in your own heritage, you’d be practicing. … You don’t practice. You should go back to your parents and say you are wasting their money. By coming back, I’m wasting my time. I should have stayed in India.”

Seated on the floor along the walls of the studio are members of his youth dance company, here for his next class. Some stare blankly ahead. Others pick nervously at their socks.

The students before him today in Fremont have their entire journey in front of them, and Das to guide them.

After giving the class a good tongue lashing, Das’ feet join the pounding with an explosion of thunderous footwork, rapid, rhythmic thumping which, even through socks, booms through the studio.

Chitresh Das is many things: A world-renowned performer, a genre-smashing collaborator, and now a father, to two-year-old daughter Shivaranjani, whose unruly tufts of curly, dark hair and deep, blazing eyes seem plucked straight from her dad.

More than anything, though, Das is a teacher. A very tough one. And a very good one.

* * *

Das has just returned from an extended trip to India, where he and tap dancer Jason Samuels Smith once again dazzled crowds with performances of their collaborative show, India Jazz Suites.

Das and Smith have danced together since meeting at the American Dance Festival in Durham, N.C. in 2004. Their first playful exchanges of dance steps backstage blossomed into an on-stage chemistry and off-stage friendship unique in modern dance.

The pair have toured together every year since 2006, performing dozens of shows together throughout North America and India.

Their relationship and uncanny symbiosis is the focus of Upaj (Improvise), a new documentary debuting Saturday night at the Computer History Museum in Mountain View. The sold-out gala premiere will include a signature performance from Das and Smith.

Driving home Thursday night from Skywalker Ranch after putting finishing touches on the movie’s audio mix, Upaj Producer Antara Bhardwaj told SFBay the project — five years in the making — has been a project of passion for all involved:

“It’s fun being at this stage of the process, where we have made a film instead of are making a film. … Sometimes it’s hard to maintain passion for a project over five years. To give you perspective, I’ve gotten married and have a one year-old son since we started working on this.”

Both Bhardwaj and Executive Producer Rina Mehta studied Kathak under Das for years, bringing a unique perspective and set of challenges to making Upaj:

“The film was conceived by (Executive Producer) Rina Mehta, also a dancer as well as myself. It’s amazing to do a film on something very dear and special to me, Kathak.”

Bhardwaj said both she and director Hoku Uchiyama came to Upaj with experience on narrative films, not documentaries:

“There was a steep learning curve for both of us. … The reality is that documentaries don’t get the kind of funding that narrative films do. We realize it’s a lot like doing a social service.”

With the final audio mix coming together just hours before the premiere, nobody will be happier to see the finished product than Bhardwaj:

“The director has put his heart and soul into this film. But I was thinking, I am going to be the most excited person in the room for the film.”

* * *

Rajashree Sarukkai watches through glass as her daughters, 11-year-old Atmika and 15-year-old Mayuka, painstakingly whirl over and over through their tihais, an elemental component of Indian classical music.

Sarukkai, from Cupertino, told SFBay the dance skills that her daughters demonstrate so gracefully is just part of the growth they’ve experienced from the guidance and philosophy of Das as their teacher:

“A true teacher should just give more than just a skill set. Every year I feel more blessed that both of my daughters are being guided. He’s a philosopher, a dance teacher, a guru. Over the years, he has done more teaching than I can do. They come home with a very different perspective. Not just dance. Real life.”

Still wiping off sweat after two and a half hours of practice, Mayuka told SFBay the energy Das brings to class makes his appearances special:

“Especially when Dadaji (Das) is in class with us, he really injects us with energy. Obviously it takes a lot of stamina. We sweat a lot. After training for a long period of time, we start feeling really rejuvenated. Then afterward, you feel really good about yourself. And I like that.”

When asked about Das’ sometimes strict approach, Mayuka said after nearly four years, she appreciates and thrives from it:

“He really keeps us on our toes. … It’s definitely effective. It really shows me just how much he cares about how well we do. He really puts out the effort.”

The biggest thing Mayuka has learned from Das, other than dance?

“Self respect. He teaches us to value ourself. It makes you feel good about yourself. We really get a feeling that in the end, we’re connecting with our culture, and that’s something we should be proud of. And also humble about.”

* * *

Of the two dozen or so students in Das’ youth class, one in particular stands out at the front of the room.

His name is Murali Meyer. He’s 10.

Murali is the only boy in his class. He’s the only boy in any of the Kathak classes all day, and one of which Murali says he doesn’t mind one bit:

“I’ve never minded if I’m the only one, because it seems to happen a lot with Kathak. In this community, I’ve just always kinda been the only one. That’s just the way it is.”

Murali was accepted into the Chhandam Youth Company’s “first years” program after two years of Kathak study followed by a challenging audition. Each year, students must successfully perform a recital to continue to advance.

Murali says he has fun with Kathak, and quickly adds:

“It’s really hard. I mean, it’s reaaaallly hard. Keeping the stamina up, you have to do it for so long, because Dadaji does it much faster than we’re used to. So even if we practice it, it’s still really hard.”

Das’ most advanced student disciples are all female, including Chhandam School co-directors Seibi Lee and Rachna Nivas, and Fremont branch director Labonee Mohanta. His dance company and all of their performances are exclusively female. Except, of course, Das himself.

Though the Chhandam School currently has six male students in Northern California out of about 500 total, Das says he is committed to maintaining an all-female dance company:

“My only regret is that I don’t have many male students. So I converted the whole thing to female power. This whole (show) is done by females. And if there’s a male student I won’t bring them in. Separate I will make it. If there are many male students, then I’ll make it. But now I will not tamper with it, and so be it.”

* * *

Born to dance teacher parents in pre-independent Kolkata in 1944, Das began his studies of Kathak and tabla before age 10.

After studying and performing under some of India’s most distinguished gurus, Das visited the United States in 1970 on a fellowship and soon settled in San Rafael, where he still calls home.

From Northern California, Das and his wife Celine oversee operations of the Chhandam school, while Das also continues to tour and travel to India multiple times each year.

Just back from his most recent sojourn, the admittedly-jetlagged Das sits on the floor of the studio — his back leaning upon the long mirrored wall — reflecting to the day’s final group of advanced students:

“Today I was watching the little children. It was a hard class. I was giving them a message: You can do it, but you’re not doing it. And why are you not doing it. Whatever I have to do to reach them, from sliding around, to goading them. This is my style I have developed over the years. I realized, the old system of a guru sitting in one area, it’s gone.”